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9/11 Day asked each of the principal presidential candidates to "suspend all campaign activity"

Clinton was New York's junior senator during the September 11 attack

Cincinnati (CNN)Both Hillary Clinton and Donald Trump's presidential campaign will stop campaign operations and airing ads on September 11 in honor of the 15th anniversary of the 2001 attacks, according to an aide.

The move comes after 9/11 Day, a nonprofit organization aiming to establish September 11 as a federally-recognized national day of service and remembrance, asked each of the principal presidential candidates -- Clinton, Republican nominee Donald Trump, Libertarian Gary Johnson and Green Party nominee Jill Stein -- to "suspend all campaign activity" to honor the day.

According to a Clinton aide, "Secretary Clinton and Sen. (Tim) Kaine will dispense with normal campaign activity on 9/11, including ceasing to run campaign advertisements."

Johnson's campaign announced Tuesday that it would not campaign on September 11 either.

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9/11 Day sent a letter to each campaign asking them to pledge to suspend all campaign activity.

The letter requested that the campaigns "dispense with normal campaign activity on that day, including ceasing to run campaign advertisements, to enable the 9/11 community and the nation to solemnly and peacefully pay tribute to the 9/11 victims, rescue and recovery workers, and those who rose to defend our nation after 9/11."

The letter also asked that rather than work on normal campaign activities, campaign staff will "dedicate time on 9/11 to remembrance and prayer, and participating in charitable service events and activities in support of the federally recognized September 11 National Day of Service and Remembrance."

Clinton was New York's junior senator during the September 11 attack and occasionally references the day and its fallout when urging Republicans and Democrats to work together.

"I remember how it felt on the day after 9/11," Clinton said during a June event in Cleveland. "And I bet many of you do as well. Americans from all walks of life rallied together with a sense of common purpose on September the 12th. And in the days and weeks and months that followed, we had each other's backs."

She added: "I was a senator from New York. There was a Republican president, a Republican governor, and a Republican mayor. We did not attack each other. We worked with each other to protect our country and to rebuild our city."